This invention relates generally to percutaneous electrical therapy systems for medical use, such as for pain treatment. In particular, the invention relates to a percutaneous electrical therapy system providing electrode depth control.
Electrical therapy; has long been used in medicine to treat pain and other conditions. For example, transcutaneous electrical nerve stimulation (TENS) systems deliver electrical energy through electrode patches placed on the surface of a patient""s skin to treat pain in tissue beneath and around the location of the patches. The efficacy of TENS systems in alleviating pain is questionable at best, however.
More recently, a technique in which electrodes are placed through the patient""s skin into the target tissue has been proposed. Percutaneous Neuromodulation Therapy (xe2x80x9cPNTxe2x80x9d) (also sometimes called Percutaneous Electrical Nerve Stimulation or xe2x80x9cPENSxe2x80x9d) using percutaneously placed electrodes achieves significantly better pain relief results than TENS treatments using skin surface electrodes. This therapy is described in Ghoname et al., xe2x80x9cPercutaneous Electrical Nerve Stimulation for Low Back Pain.xe2x80x9d JAMA 281:818-23 (1999); Ghoname et al., xe2x80x9cThe Effect of Stimulus Frequency on the Analgesic Response to Percutaneous Electrical Nerve Stimulation in Patients with Chronic Low Back Pain,xe2x80x9d Anesth. Analg. 88:841-6 (1999); Ahmed et al., xe2x80x9cPercutaneous Electrical Nerve Stimulation (PENS): A Complementary Therapy for the Management of Pain Secondary to Bony Metastasis,xe2x80x9d Clinical Journal of Pain 14:320-3 (1998); and Ahmed et al., xe2x80x9cPercutaneous Electrical Nerve Stimulation: An Alternative to Antiviral Drugs for Herpes Zoster,xe2x80x9d Anesth. Analg. 87:911-4 (1998). The contents of these references are incorporated herein by reference.
Thus far, PNT practitioners have used percutaneously placed acupuncture needles attached to waveform generators via cables and alligator clips to deliver the therapy to the patient. This arrangement and design of electrodes and generator is far from optimal. For example, the prior art has not addressed the issue of how to accurately control the depth of insertion of electrical therapy electrodes. It is therefore an object of this invention to provide electrode depth control for electrical therapy systems.
It is a further object of this invention to provide a percutaneous electrical therapy system having electrodes and electrode assemblies that are safe, efficacious, inexpensive and easy to use.
Other objects of the invention will be apparent from the description of the preferred embodiments.
The invention is a percutaneous electrical therapy system with electrode angle of entry control. In a preferred embodiment, the system includes a control unit; an electrode assembly adapted to deliver electrical therapy to a patient, the electrode assembly including an electrode electrically connectable to the control unit, the electrode having a sharp point at a distal end adapted to be inserted into a patient""s tissue; and an electrode depth control assembly adapted to control insertion of the electrode""s point to a predetermined depth into the patient""s tissue. In preferred embodiments, the electrode depth control assembly has a limit stop limiting length of travel of the electrode""s point. In these embodiments, the electrode depth control assembly further may also include an electrode actuator, the limit stop limiting movement of the electrode actuator. In some embodiments, the electrode assembly includes a housing, with the housing forming a limit stop.
In one embodiment, the system includes an actuator tool adapted to interact with the actuator to move the electrode""s sharp point into the patient""s tissue. The actuator tool may be further adapted to remove the sharp point of the electrode from the patient""s tissue. The actuator tool may also have an electrical contact adapted to make electrical communication between the electrode and the control unit.
In some embodiments, the system includes an electrode introducer adapted to insert the electrode into the patient and release the electrode, wherein the electrode introducer forms part or all of the depth control assembly. In these embodiments, the electrode introducer may include an actuator cooperating with the limit stop, the actuator being adapted to move the sharp point of the electrode into the patient""s tissue. The system may also have a transmission assembly adapted to insert the electrode""s point the predetermined depth into the patient""s tissue when the actuator is moved a predetermined actuator distance, the predetermined depth being greater than the predetermined actuator distance. For example, the transmission assembly may transmit linear movement of the actuator into linear movement of the electrode.
In some embodiments, the electrode depth control assembly has an electrode holder adapted to be mounted on the patient and to interact mechanically with the electrode. For example, the electrode holder may be an adhesive patch and/or an opening adapted to surround the electrode when the electrode has been inserted into the patient""s tissue. The electrode depth control assembly further may also include a handle portion on a proximal end of the electrode.
In some embodiments, the electrode assembly also includes a deployed electrode holding mechanism adapted to hold the electrode in place after insertion of the sharp point of the electrode into the patient""s tissue.
In some embodiments, the electrode assembly also includes an electrode insertion axial stabilizer adapted to provide axial stability to the electrode during insertion of the sharp point of the electrode into the patient""s tissue.
In some embodiments, the electrode assembly also includes an electrode insertion pain reducer adapted to reduce pain experienced by the patient during insertion of the sharp point of the electrode into the patient""s tissue.
In some embodiments, the electrode assembly also includes an electrode angle of entry controller adapted to control the electrode""s entry angle during insertion of the sharp point of the electrode into the patient""s tissue.
The invention also includes the percutaneous electrode and depth control assembly described above apart from the control unit.
The invention is also a method of performing percutaneous electrical therapy, the method including the steps of providing an electrode assembly comprising an electrode, the electrode having a sharp point at a distal end; using an electrode depth control assembly to insert the sharp point of the electrode a predetermined depth into a patient""s tissue; and applying an electrical signal to the electrode from a control unit. The method may also include the step of moving an actuator a predetermined actuator distance, the actuator moving the electrode to insert the sharp point of the electrode into the patient""s tissue. In one embodiment, the predetermined actuator distance is less than the predetermined depth. The moving step may include the step of moving the actuator until actuator movement is limited by a limit stop.
In some embodiments, the using step includes the step of using an introducer to insert the sharp point of the electrode into the patient""s tissue, the introducer comprising the electrode depth control assembly. The using step may include the step of releasing the electrode from the introducer.
In some embodiments, the using step includes the step of mounting an electrode holder on the patient and mechanically interacting the electrode with the electrode holder. The mechanically interacting step may include the step of inserting the electrode through an opening in the electrode holder.
In some embodiments, the using step includes the step of using an actuator tool to move an actuator, the actuator moving the electrode to insert the sharp point of the electrode into the patient""s tissue. These embodiments may also include the step of using the actuator tool to remove the sharp point of the electrode from the patient.
The method may also include the step of making an electrical connection between the electrode and the control unit.
The method may also include the step of supporting the electrode in the patient""s tissue after the inserting step.
In some embodiments of the method, the inserting step includes the step of using the electrode assembly to guide electrode entry angle.
In some embodiments of the method, the inserting step includes the step of using an introducer to guide electrode entry angle.
In some embodiments of the method, the inserting step includes the step of providing axial stability to the electrode during insertion.
In some embodiments of the method, the inserting step includes the steps of placing a housing adjacent the patient""s tissue; and moving the sharp point of the electrode out of the housing and into the patient""s tissue. These embodiments may include the step of placing a patch on the patient""s tissue prior to the step of placing a housing, the step of placing a housing including the step of placing the housing adjacent the patch. In some embodiments, the patch may have an opening, with the moving step including the step of moving the sharp point of the electrode out of the housing, through the opening and into the patient""s tissue. Some embodiments may include the step of mechanically supporting at least a portion of the electrode with the patch.
In some embodiments, the moving step includes the steps of moving the entire electrode out of the housing; and removing the housing from the patient""s tissue.
The invention is described in further detail below with reference to the drawings.